MINNEAPOLIS -- Percy Harvin is back on the football field, and he thinks doctors finally have found the root of the problem that's kept him off of it, too.

"I did a test (Friday) night," Harvin said after the Minnesota Vikings' 24-13 exhibition win over the Seattle Seahawks.

"They found some things that we think is the main cause of it. We're all feeling really confident. I know we said that a couple times, but I think this time we found what the main cause was. I'm not saying I won't ever get a headache again, but hopefully, we can slow it down a little bit."

That would be good news for the Vikings and Harvin, who hadn't done much of anything on the field since his Aug. 19 collapse and hadn't been cleared to resume football activities as of Thursday afternoon.

But there was Harvin in Saturday night's 24-13 preseason win against the Seattle Seahawks, lining up in the slot on the Vikings' first play and catching a Brett Favre pass for a 34-yard gain.

"It was tough, but that's part of life," Harvin said. "We've got a great plan coming up here, so I think everything should be behind me."

Harvin declined to say what doctors discovered -- head athletic trainer Eric Sugarman recently said an adverse reaction to medication was one of several possible factors -- or where he underwent the final test, saying only, "We did find something. It's not life-threatening, but it's something that we need to work on, and we will."

Three hits tested Harvin's recovery -- one on a pass he bobbled into a near-interception, one on a bubble screen that lost 4 yards and another on his final play, when he got up slowly after colliding in pattern with Seahawks safety Earl Thomas.

Linebacker Aaron Curry's tackle on the screen sent Harvin's helmet flying, leading to a brief exchange between Harvin and veteran Seattle safety Lawyer Milloy.

"Everybody looks for that first contact, to get hit, kind of feel a part of the game," Harvin said. "So, I was looking forward to getting hit. That was the main thing, getting contact, getting used to catching the ball out there, things like that."

For a player who missed most of training camp and the first two preseason games because of migraine headaches -- including the Aug. 19 episode that sent him to the hospital -- Harvin's mere presence on the field was rather startling.

In addition to the migraines, there were concerns about whether Harvin was in game shape after all the practice he'd missed. The need to get in some work with the starting offense apparently outweighed those concerns, though, leading to Harvin getting around a dozen snaps.

"I would like to see him more active in the offense," coach Brad Childress said. "There are some signs of rust -- you can tell from some of those routes he ran. It's just good to see his smiling face out there. He didn't seem any worse for the wear. He took a couple pretty good licks."

Like many other starters, Harvin may have nearly two full weeks to recover. Most starters are expected to sit out Thursday's preseason finale against Denver.

"I've got a lot of work to do as far as condition-wise," Harvin said. "But otherwise, it just felt good to get out there and have something to base my performance off of."